<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>事件类型</title>
</head>
<body>
    <input id="input" type="text">
    <select name="" id="select">
        <option value="">123</option>
        <option value="">234</option>
        <option value="">345</option>
    </select>
</body>
<script>
    // var app = document.getElementById("app");
    // window.onload = function() {
    //     alert(999)
    // }

    var input = document.getElementById("input");

    // input.onselect = function(event) {
    //     console.log("有文本被选中");
    // }

    // var select = document.getElementById("select");

    // select.onchange = function() {
    //     alert(999)
    // }
    // window.onresize = function() {
    //     alert('窗口大小已经发生变化')
    // }

    // input.onblur = function(event) {
    //     console.log('鼠标已经失焦');
    // }
    input.onfocus = function(event) {
        console.log('鼠标已经具焦');
    }
</script>
</html>